Photographic silver halide emulsions



United States Patent O 2,965,487 PHOTOGRAPHIC SILVER HALIDE EMULSIONS Thomas David Smith, Red Bank, NJ assignor to E. l. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. FiledDec. 14, 1959, Ser. No. 859,108 13 Claims. (Cl. 96-107) This invention relates to photography, and more particularly to photographic silver halide emulsions containing a non-optical sensitizing agent having at least one polyoxyalkylene group containing at least two oxyalkylene radicals. Still more particularly, it relates to such emulsions containing a hydrocarbon-substituted mononuclear monohydric phenol of at least ten carbon atoms wherein the hydrocarbon substituent is in one of the positions ortho or meta to the hydroxyl groups and the other positions are unsubstituted. The invention also relates to photographic elements, e.g., films and papers, bearing at least one layer of such an emulsion.

It is known that photographic silver halide emulsions which have been sensitized to very high levels tend to produce fog on development. This photographic fog is due to the existence in the emulsion of silver halide grains which are developable without exposure to light. In addition, fog may be produced in photographic emulsions during storage, particularly under adverse conditions of temperature and humidity.

As is well known, the sensitivity of photographic emulsions can be increased in a number of ways. One of these is by adding derivatives of alkylene oxides, such as polyethylene oxide or condensation products of polyethylene oxide with acids, alcohols or amines such as taught, for instance, by Blake et al., US. 2,400,532; Blake, US. 2,423,549; Blake, US. 2,441,389, and Carroll et al., 2,716,062. However, these compounds tend to cause fog when photographic materials, the emulsions of which contain them, are stored for any length of time. Attempts to reduce this fog have involved the use of antifogging agents which are frequently detrimental to certain photographic properties. In particular, such antifoggants tend to reduce the photographic speed of film exposed to'relatively low intensity illumination.

It is therefore an object of this invention to provide means for reducing fog in photographic emulsions. Another object is to reduce fog produced on storage of emulsions, particularly in tropical climates or under other adverse conditions of temperature and humidity. A further object of this invention is to provide silver halide emulsions sensitized with alkylene oxide polymers of im proved stability and less tendency to'form an objectionable amount of fog on normal storage of photographic elements embodying such emulsions. Still other objects are to achieve the above results without reducing speed or contrast and, in particular, without reducing the speed of the emulsion to low intensity illumination.

The above objects are attained and photographic emulsions and emulsion layers of good stability, speed and contrastwhich exhibit low fog values upon aging at normal temperatures for extended periods are provided, in accordance with the invention, by admixing relatively small amounts of at least one hydrocarbon-substituted mononuclear monohydric phenol of at least nine carbon atoms wherein said substituent is in the ortho or meta position to the phenolic hydroxyl group, with a photographic silver halide emulsion containing sensitizing amounts of a nonoptical or chemical emulsion sensitizing agent having a of these types.

2,955,487 Patented Dec. 20, 1960 2 molecular weight of at least 282 and containing at least two, and preferably at least six, oxyalkylene units of two to four carbon atoms.

The mononuclear monohydric phenols used in accordance with the invention can be represented by the general formula:

wherein one of the radicals R and R is hydrogen and the other is a hydrocarbon radical of at least 3 carbon atoms. The hydrocarbon radicals may be alxyl, cycioalkyl, aryl and arallcyl. The alhyl radicals may contain 3 to 12 or more carbon atoms and suitable alxyl radicals are tbutyl, sec-amyl, t-amyl and t-octyl, n-honyl and n-dodecyl. Suitable cycloalkyl radicals are cyctopentyl and cyclohexyl. Useful aryl radicals include phenyi', naphthyl and bipnenyl. Suitable aralkyl radicals include benzyl, pt-cutnyl and naphthylmethyl.

in an important specific embodiment of the invention the hydrocarbon-substituted mononuclear monohydric phenols have a hydrocarbon substituent attached to the nuclear carbon atom through ,a saturated hydrocarbon radical which is attached to at least two additional hydrocarbon radicals. Suitable such substituents are isoalkyl, t-alkyl and cycloalkyl.

it has been discovered that when 5 to 50 millimoles of at least one hydrocarbon substituted mononuclear monohydric phenol .of the type described above is used per the resulting emulsions remain substantially at the initial values of the emulsion prior to the addition of said phenol,

even when the emulsions or emulsion layers are maintained under adverse storage conditions for a short or extended period of time, e.g., at an elevated temperature and/or under conditions of high humidity.

The invention is not limited to any particular type of light-sensitive silver halide as it is useful with silver chloride, silver bromide, silver iodobromide, silver chlorobromide, silver iodide, etc., emulsions and mixed emulsions it is particularly etfi-acious in silver iodobromide emulsions containing about 2 mole percent iodide and the rest bromide. These emulsions may be sensitized by means of chemical sensitizing agents other than the polyoxyalkylene polymers mentioned above. Thus, noble metal sensitizers, e.g., gold salts, e.g., chlorauric acid and auric trichloride, may be present in association with sulfur sensitizers, e.g., sodium sulfite, thiosinamine, allylthiourea, sodium thiosulfate, allyl thiocarbamate, alkali metal thiocyanates and sodium sulfide, these sensitizers to be used in amounts up to 0.005% based on the weight of the silver halide. Moreover, the silver halide emulsions may contain one or more optical sensitizing agents, e.g., cyanine, carbocyanine, merocyanine, pseudocyanine, cyazine etc., ,dyes.

With regard to the non-optical sensitizers which contain at least one polyoxyalkylene group, there are a relatively large number of such compounds known to the art, suitable compounds being described in the above patents. These compounds include not only the polyalkylene oxides or glycols wherein the oxyalkylene groups contain 2 to 4 carbon atoms but also the condensation products of alkylene oxides of 2 to 4 carbon atoms with glycols, fatty acids, saturated aliphatic amines, and hexitol ring dehydration products, said compounds having a molecular weight of at least 282, suitable specific compounds of which are disclosed in the aforesaid patents. In general,

3 these sensitizing compounds are present in amounts from 0.1 to 2.0 g. per mole of silver halide.

While gelatin is the preferred binding agent for the silver halide grains, other water-permeable amphoteric protein protective colloids, e.g., albumin and casein, can be used. Also, agar-agar, alginic acid and the alginates, polyglycuronic acid, polyvinyl alcohol, polyvinyl acetals including those containing color-forming nuclei, and other natural or synthetic water-permeable colloids useful in making photographic emulsions can be used as the original colloid during the precipitation, or in the final emulsion as bulking agents.

The hydrocarbon-substituted mononuclear monohydric phenols are p eferably added to the silver halide emulsion after it has been brought to its maximumsensitivity and the conventional adjuvants are added just prior to coating onto a suitable support to form a photographic element. They can. of course. be added at an earlier stage, that is, at the time of second digestion.

The invention will now be further illustrated by but is not intended to be limited to the folowing examples,

wherein the silver halide weight ratio, unless otherwise indicated, is 1.6 mole percent iodide and the remainder bromide. In these examples the emulsions were prepared and coated in the essential absence of actinic radiation, as is customary in the photographic art.

Example I polyethylene oxide per mole of silver halide together with 20 millimoles of o-benzylphenol (II).

The coatings were tested fresh, after one month of room aging, and after one week at 120 F. and 65% RH. (relative humidity). The exposed photographic films were then processed (a) by being developed for 5 minutes in a developer of the following composition:'

Grams N-methyl-p-aminophenol hydrosulfate 3 Anhydrous sodium sulfite Hydroquinone 9 Anhydrous potassium carbonate 50 Potassium bromide 4.5

Water to make 1000 ml.

and (b) by being fixed for 5 minutes in a fixing solution of the following composition:

Sodium thiosulfate, anhydrous grams 153 Sodium sulfite, anhydrous do 15 Borax do 18 Glacial acetic acid ml 12 Potassium alum (l2l-l O) "grams" 20 Water to make 1 liter.

Results of tests for speed, gamma and fog, before and after storage treatment of the samples are given'below. Speed is given in terms of a reciprocal of exposure at a density of 0.7. If fog is greater than 0.40 the speed and gamma numbers are of no significance and are therefore not included in such cases.

[Fresh results] [One month room aging] i one week anon F. and 65% RH. (Relative humidlty)] Fog IControl I plus II Moon mas-c- Example 2 A gelatino-silver iodobromide emulsion, digested with sulfur and gold compounds, was divided into three portions. One portion was treated with .53 g. of (l) the polyethylene oxide described in Example 1 per mole of silver halide. To a second portion was added .53 g. of the polyethylene oxide together with 20 millimoles of (II) o-phenylphenol per mole of silver halide. Coating, exposure, processing and aging were carried out as in Example 1.

[One week at. F. and 65% R.H.]

sulfur and gold compounds, was divided into three portions. One portion was treated with 1.1 g. of the condensation products of polyethylene oxide with oleyl a'cohol (I) having a molecular weight of approximately 900 (Emulphor ON-870 manufactured by the Antara Chemicals Division, General Aniline and Film Corp.), per mole of silver halide. To a second portion was added 1.1 g. of the above condensation product together with-20 millimoles of o-phenylphenol (11) per mole of silver halide.

Coating. exposure, processing and aging were carried out as in Example 1.

[Fresh results] densation product of Example 3 per mole of silver halide. To a second portion there was added 0.5 g. of the above cond sation product per mole of s lve hal tog with 10-milli1rioles ofmpyqlohexylphenol.

NmzExposure Na 1 Exposure 5 Coating, exposure, processin and aging were carried Compound Amount per og outas infixample 1.

Speed Gamma Speed Gamma {Freshresults} Control None 690 2.54 4 80 2.19 .37 No.2Exposure No.1.Exposure .48 10 Compound Amount per Fog atelolcyl 1 I mole 1 alcohol I. .Speed Gamma Speed Gamma lplus I1 1.111.120 milll- 890 2.65 550 2.28 .36 g

mo es. 1 p 1 1 Control none 720 2.40 420 2.40 .25 I polyoxy- 0.5 e .50 [Onemonth room aging] 1 ethylated 5 ole alcohol. No. 2 Exposure No. 1 Exposure I plus IL-.. 05g. m llll- 910 2. 49 360 2. 49 21 Compound 7 Fog 1 moles;

Speed Gamma Speed Gamma 0 {One month room aging] 22 a 23s e s. ,No.,2 Exposure No.1 Exposure lplus II 880 2. 43 500 1.83 .20 compound V Fog [One eek at 120 F. and 65% R.H.] speed Gamma sl'jeed Gamma a ""5116 "2.11? ""556 2 :6? :18 Control .57 I 90 I plus II .42 [,(Jne week at. 120 Rand 65% R.H.]

Example4 Fog A gelatino-si'ver iodobromide emulsion, digested with l 4 sulfur and gold compounds, was divided into three pqrf??? 1 :3 tions. One portion was treated with 0.5 g. of the poly- Iplus II- .38 oxyethylated oleyl alcohol condensation product (I) of Example 2 per mole of silver halide. To a second por- Exam la 6 *tion was added 0.5 g. of the above condensation product 1 p per mollle ofI sfilverlh'iiiide together w1th 20 m1ll1moles of A gelatinmsilvfir iodobmmidle emulsion digested with exy P @110 40 sulfur and gold compounds, was divided into three por- Coating, exposure, out as in Example 1.

processing and aging were carried [Fresh res ults] tions. One portion was treated with 0.5 g. ethylene .oxide of Example 1 (I) per mole of To ajsecond portion was added 0.5 g. of the of the polysilver halide. polyethylene .oxide per moleof silver halide together with 20 milli- N0-2EXD0S11re NOIEXPOSIIYQ moles of m-phenylphenol' (II). Neither of these addi' Compound 1 Amount per Fog mole t1ons was made to a thlrd port1on. Coatmg, expo-sure, Speed Gamma Speed (3mm? processing, and aging were carried out as in Example 1. Control None 690 2. 54 480 2. 19 :37 .l results] :lporllyrixgr-d 0.5 g .48 V l egl e i No. 2 Exposure No. 1 Exposure 1 alcohol. 1 Compound Amount per Fog 1 II 0. .20 n 10 2.45 490 2. 5 .27 11108 'Ipus m oles. 1 3 Speed Gamma Speed Gamma Control 860 2. 70 380 2. 34 15 month room s l 55 I 0.5 g 1,010 2. 35 490 1.91 .36 Iplus II 0.5 .20m1u1- 720 2.76 .420 2.54 .15

0 68. N o. 2 Exposure No. 1 Exposure m Compound Fog Speed Gamma Speed Gamma. month mom agmg] Control 670 2. 25 400 1.93 .23 No.2 Exposure No. 1 Exposure 1850 2. 5s 200 2. 0 .aa Compound Fog J .1 1. Iplusl 880 40 9 6 Speed Gamma Speed Gamma mm F.. (165 RH. l [Onewem an 1 Conn-o1 700 2.19 320 2.11 Fog 700 2.31 ""556' 1. 99 I10 [One week at 1 0 F. and 12.11.

' Fog Example5 I I A gelatzno-silver lodobromide emulsion, dlgestedwnh :33 .sulfur and gold compounds, was divided into three por- -P 1 .32

'tions. One portion was treated with 0.5 g. of the con- I three portions.

pound (I) of Example 3.

Example 7 A gelatino-silver iodobromide. emulsion, digested with sulfur and gold sensitizing compounds, was divided into One portion was treated with 0.5 g. of

the polyethylene oxide compound (I) of'Example 1' per mole of silver halide. A second portion was treated with (I) and 20 millimoles of m-tertiary butyl phenol (11).

Neither of these additions was made to a third portion of the emulsion.

Coating, exposure, processing and aging were carried out as in Example 1 except that the aging was for 2 A gelatino-silver iodobromide emulsion, digested with sulfur and gold sensitizing compounds was divided into three portions. One portion was treated with, 0.5 g. per mole of silver halide of .the polyethylene oxide com- To a second portionthere was added 0.5 g. of (I) and 20 millimoles .of o-isopropylphenol (11) per mole of silver halide. Neither of these additions was made to the thirdportion. Coating,

exposure, processing and aging were carried'out as in Example 7. A

[Fresh results] No. 2 Exposure No. 1 Exposure Compound Amount per Fog mole ' Speed Gamma Speed Gamma Control none- 46 0.5g .58 1 plus II 0.5 g. 20 milli- 830 3. 31 400 2. 75 .40

I moles.

W [Two months aging] No. 2 Exposure No. 1 Exposure Compound Fog Speed Gamma Speed Gamma In place of the specific hydrocarbon-substituted inononuclear monohydric phenols used in the foregoing ex amples there maybe substituted one or more other such compounds falling within the" 'generic""characterization given above. Suitable additional compounds include "ortho-n-butylphenol, orthmbbutylphenol, and" o-sec=amylphenol. digestion and after addition of the polyoxyalkylene sen'sitizing compound. At the-same-time othercompounds These compounds are generally added after having antifogging properties can be added to the emulexpensive chemicals or tedious procedures.

available chemical compounds.

-- sane sions. Suitable antifogging agents which can be used include benzotriazole, nitrobenzimidazole, l-phenyl-S- mercaptotetrazole, and benzothiazole.

The resulting photographic emulsions can be coated onto any suitable support to make the desired type of photographic element. Suitable supports include cellulose esters, e.g., cellulose acetate, cellulose nitrate, cellulose acetate butyrate, cellulose propionate; super poly mers, e.g., nylon, polyethylene terephthalate, polyvinyl chloride, poly(vinyl chloride co vinyl acetate) and vinylidene chloride copolymers with vinyl acetate, acrylonitrile, etc.; metal sheets or foils, e.g., aluminum and zinc; and paper including resin-coated and baryta-coated paper; as well as glass plates, inter alia.

An advantage of this invention is that it provides photographic emulsions and elements with improved stability and aging characteristics. It enables one to obtain the useful sensitizing action of the polyoxyalkylene compounds without an undue degree of fog being formed upon storage of the photographic elements for long periods.

Another advantage is that the improved emulsions and emulsion layers can be made by the addition of readily A further advantage is that the improved emulsions do not require the use of A still further advantage is that the speed of the aforedescribed silver halide emulsions to light of various intensities is not affected to the same degree as known non-phenolic antifogging agents. A related advantage is that while the hydrocarbon-substituted mononuclear monohydric phenols have an antifogging action in photographic silver halide emulsions sensitized with amphiphilic comsignificant affect on other contrast, graininess, resopounds, they do not have a photographic properties, e.g.,

'lution, optical sensitization and latent image stability.

This application is a continuation-in-part of my copending application Ser. No. 656,181, filed May 1, 1957.

What is claimed is:

1. A water-permeable colloid silver halide emulsion containing per mole of silver halide (1) from 0.1 to 2.0 grams of a non-optical sensitizing agent having a molecu- --lar weight of at least 282 and containing at least one polyoxyalkylene group having at least two oxyalkylene radicals of 2 to 4 carbon atoms taken from the group consisting of condensation products of alkylene oxides of 2-4 carbon atoms with glycols, fatty acids, saturated aliphatic amines and hexitol ring dehydration products and (2) from 5 to millimoles of a hydrocarbon-substituted mononuclear monohydric phenol of at least 9 carbon atoms wherein the hydrocarbon substituent contains 3 to 12 carbon atoms and is in one of the positions orthoand metato the hydroxyl group and the other positions of the benzene ring are unsubstituted.

2. An emulsion as set forth in claim 1 wherein said hydrocarbon substituent is an alkyl radical of 4 to 12 carbon atoms.

3. An emulsion as set forth in claim 1 wherein said hydrocarbon substituent is a cyclohexyl substituent.

4. An emulsion as set forth in claim 1 wherein said silver halide is an iodobromide.

5. An emulsion as set forth in claim 1 wherein said sensitizing agent is a polyethylene oxide having an average molecular weight of at least 1500.

. 6. An emulsion as set forth in claim 1 wherein said agent is a condensation product of ethylene oxide with I oleyl alcohol.

7. An emulsion as set forth in claim 1 wherein said phenol is o-benzylphenol.

8. An emulsion as set forth in claim 1 wherein said phenol is o-phenylphenol.

9. -An emulsion as set forth in claim 1 wherein said phenol is rn-tertiary butylphenol.

10. An emulsion as set forth in claim 1 wherein said colloid is gelatin.

11. A photographic element comprising a support having at least one layer composed of a photographic emulsion as set forth in claim 1.

12. An element as set forth in claim 11' wherein said support is a hydrophobic film base.

13. An element as set forth in claim 11 wherein said support embodies a polyethylene terephthalate film base.

References Cited in the file of this patent UNITED STATES PATENTS Middleton et al. Feb. 15, 1944 Blake May 11, 1948 Gunther Apr. 29, 1952 Vaughn et al. May 13, 1952 Reynolds et al. July 24, 1956 

1. A WATER-PERMEABLE COLLOID SILVER HALIDE EMULSION CONTAINING PER MOLE OF SILVER HALIDE (1) FROM 0.1 TO 2.0 GRAMS OF A NON-OPTICAL SENSITIZING AGENT HAVING A MOLECULAR WEIGHT OF AT LEAST 282 AND CONTAINING AT LEAST ONE POLYOXYALKYLENE GROUP HAVING AT LEAST TWO OXYALKYLENE RADICALS OF 2 TO 4 CARBON ATOMS TAKEN FROM THE GROUP CONSISTING OF CONDENSATION PRODUCTS OF ALKYLENE OXIDES OF 2-4 CARBON ATOMS WITH GLYCOLS, FATTY ACIDS, SATURATED ALIPHATIC AMINES AND HEXITOL RING DEHYDRATION PRODUCTS AND (2) FROM 5 TO 50 MILLIMOLES OF A HYDROCARBON-SUBSTITUTED MONONUCLEAR MONOHYDRIC PHENOL OF AT LEAST 9 CARBON ATOMS WHEREIN THE HYDROCARBON SUBSTITUENT CONTAINS 3 TO 12 CARBON ATOMS AND IS IN ONE OF THE POSITIONS ORTHO- AND META- TO THE HYDROXYL GROUP AND THE OTHER POSITIONS OF THE BENZENE RING ARE UNSUBSTITUTED. 